The “cons” were that she was fired.
Somers was let go, and spent a short period of time in “exile” from mainstream television until (ironically) she was again hired for an ABC network sitcom called Step By Step where she spent six years (the final season was moved over to CBS) and she arguably earned far more than ABC would have had to pay her had she remained on Three’s Company.
The “pros” for Somers is that her departure proved her point: The show needed her.
Every episode after Somers left the program is frankly terrible. Neither one of the TWO replacement blonde actors who they hired could compete with Somers timing and screen presence. And neither John Ritter, nor Joyce DeWitt, (the other two of the titular THREE) were able to carry the program successfully without Somers to riff off of. By the time the series ended, things were so terrible that the spinoff it created, Three’s A Crowd, crashed and burned simply because there was not much to it.
Somers was the breakout character and the “heart” of Three’s Company.
Firing her was the biggest “con” of them all.
We’ll miss you Suzanne: